Influence of psychological stress on Systolic-Diastolic Interval (SDI) interaction characteristics measured from the electrocardiogram (ECG) signal

Abstract

Stress affects the ventricular repolarization and the ventricular mechanical function by increasing the QT interval variability and changing left ventricular ejection fraction respectively. As QT and TQ intervals are considered as surrogates of mechanical systolic and diastolic durations, alteration of QT and TQ interval dynamics can be used to analyse stress related changes in the systolic and diastolic function of the heart. The ratio of QT to TQ interval within a cardiac cycle (i.e. QTTQ ratio) represents the synchronized contraction and relaxation operation of the heart. Besides QTTQ, the ratio of TQ to RR interval (i.e. TQRR ratio) can also be used as a non-invasive measure of the diast..